Carotenoids are a large class of isoprenoid pigments synthesized by all photosynthetic organisms, as well as some bacteria, fungi, and aphids (Cuttriss et al., Adv. Botanical Res. Part A 58:1-36, 2011). In plants, carotenoids serve essential roles in photosynthesis and photoprotection (Jahns et al., Biochim. Biophys. Acta Bioenergetics 1817:182-193, 2012), and are precursors to apocarotenoids that function in stress and developmental responses (Walter et al., Planta 232:1-17, 2010).
Plant-derived carotenoids also provide nutritional benefits to humans. For example, lutein is a natural part of the human diet when fruits and vegetables are consumed. Lutein-fortified foods are available for individuals lacking sufficient lutein intake. While there is no recommended daily allowance for lutein, the positive effects of lutein can be observed at dietary intake levels of 6-10 mg/day. In addition to its use in nutraceuticals and fortified food products, lutein can be used to treat age-related macular degeneration and other eye diseases, or as an antioxidant (e.g., used as an antioxidant in cosmetic agents).